Stentor (ciliate)

Stentor, sometimes called trumpet animalcules, are a genus of filter-feeding, heterotrophic ciliates, representative of the heterotrichs. Stentor is a ciliate. They are usually horn-shaped, and reach lengths of two millimeters; as such, they are among the largest known extant unicellular organisms. They reproduce asexually through binary fission.[1]

Stentor
Stentor roeselii
Scientific classification
Kingdom: Chromista
Superphylum: Alveolata
Phylum: Ciliophora
Class: Heterotrichea
Order: Heterotrichida
Family: Stentoridae
Carus, 1863
Genus: Stentor
Oken, 1815
Species
  • Stentor amethystinus
  • Stentor araucanus
  • Stentor baicalius (syn. Stentor pygmaeus)
  • Stentor barretti
  • Stentor caudatus
  • Stentor coeruleus
  • Stentor cornutus
  • Stentor elegans
  • Stentor fuliginosus
  • Stentor igneus
  • Stentor introversus
  • Stentor katashimai
  • Stentor loricatus
  • Stentor magnus
  • Stentor muelleri (syn. Stentor felici)
  • Stentor multiformis (syn. Stentor gallinulus, =Stentor nanus)
  • Stentor multimicronucleatus
  • Stentor niger
  • Stentor polymorphus (syn. Stentor pediculatus)
  • Stentor pyriformis
  • Stentor roeselii

Description

The body, or cortex, is generally horn-shaped, hence the association with the Greek herald, and the former name "trumpet animalcule". A ring of prominent cilia around the anterior "bell" sweep in food and aid in swimming. Some reach several millimeters in length, making them among the largest single-celled organisms. Stentor can come in different colors: for example, S. coeruleus can appear blue due to the presence of stentorin, a natural pigment. As in many freshwater protozoans, Stentor has a contractile vacuole. Because the concentration of salt inside the cell and in the surrounding freshwater is different, Stentor must store water that enters it by osmosis and then discharge it from the vacuole. They can regenerate, and small fragments can grow into full organisms. Each cell has one (often elongated) macronucleus and several micronuclei.

  • Stentor polymorphus with algal symbionts
  • Stentor polymorphus with algal symbionts
  • Stentors settled on water milfoil leaf

Ecology

These protists are common worldwide in freshwater lakes and streams; only S. multiformis has been recorded from marine, freshwater, and even terrestrial biotopes. They are usually attached to algal filaments or detritus. Some Stentor species, such as S. polymorphus, can live symbiotically with certain species of green algae (Chlorella). After being ingested, the algae live on while their host absorbs nutrients produced, whereas the algae, in turn, absorb and feed on the Stentor's metabolic wastes. Stentor species react to outside disturbances by contracting into a ball. Resting cysts are known from a few species.[2]

Systematics

The genus contains over twenty described species (see list in box).[3][4] The genus Stentor was named in 1815 by the German biologist Lorenz Oken (1779–1851).[5]

The type species of the genus is Stentor muelleri Ehrenberg, 1831. According to recent molecular analyses, the genus seems to be monophyletic, and related to the genus Blepharisma.[6]

Stentor muelleri in mucous lorica
Stentor coeruleus dividing (binary fission)
Stentor muelleri, magnified 1000X

References
  1. "Stentor". Microbewiki.kenyon.edu. Retrieved June 20, 2014.
  2. Tartar, Vance (1961). The biology of Stentor. International series of monographs on pure and applied biology: Division, Zoology. Vol. 5. Pergammon Press. OCLC 558125.
  3. Kumazawa, H. (2002). "Notes on the taxonomy of Stentor Oken (Protozoa, Ciliophora) and a description of a new species". J. Plankton Res. 24 (1): 69–75. doi:10.1093/plankt/24.1.69.
  4. Foissner, W.; Wölfl, S. (1994). "Revision of the genus Stentor Oken (Protozoa: Ciliophora) and description of S. araucanus nov. spec. from South American lakes". J. Plankton Res. 16 (3): 255–289. doi:10.1093/plankt/16.3.255.
  5. See:
    • Oken, Lorenz (1815). Okens Lehrbuch der Naturgeschichte. Dritter Theil: Zoologie. Erste Abtheilung: Fleischlose Thiere [Oken's Textbook of Natural History. Third Part: Zoology. First Section: Flesh-less Animals.] (in German). Leipzig, (Germany): C.H. Reclam. p. 45. From p. 45: "4 Gattung. Trichtel, Stentor; Leib gestielt, Mundrand umgelegt, durchsichtig. Sitzt gewöhnlich mit dem Stiel fest an Wasserlinsen, meist in Gesellschaft." (4th genus. Little funnel, Stentor; stalked body, rim of the mouth is wrapped around, transparent. Usually sits with the stalk fastened to duckweed, mostly in colonies.)
    • Aescht, Erna (2001). Catalogue of the Generic Names of Ciliates (Protozoa, Ciliophora) (PDF). Linz, Austria: Biologiezentrum des Oberösterreichischen Landesmuseums (Center for Biology of the State Museum of Upper Austria). pp. 153, 251, 307.
  6. Gong YC, Yu YH, Zhu FY, Feng WS (2007). "Molecular phylogeny of Stentor (Ciliophora: Heterotrichea) based on small subunit ribosomal RNA sequences". J. Eukaryot. Microbiol. 54 (1): 45–8. doi:10.1111/j.1550-7408.2006.00147.x. PMID 17300519. S2CID 39515796.
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